Crikey, that's a collection of injuries
- all the best for a good recovery !
Will the spinal fracture heal at some point and be less of a liability ?
I ride a recumbent - tho' it's actually a 2-wheeler with a lower seat height than many - and certainly it gives the back a lot of support. There's three main variations on seat types and I'm sure you'd find one that would suit your back or could be adjusted/padded to fit : profiled hard shell (eg ICE, raptobike, Nazca, Optima) or aluminium sheet (Challenge) in different sizes; webbing style (Greenspeed, Catrike, ICE); two-part adjustable (HPVelotechnik)
A few pros and cons:
Generally they're a bit heavier than uprights, often16-18kg (unless you look at the Challenge Recumbents SL models, they're 2-wheelers and can be bought at about the 22lbs mark)
The muscle usage is a little different to an upright - that might affect you to some degree with a missing glut, but the only answer would be to try one out.
On hills you just have to find the right gear and spin - on the other hand, on rolling hills you can sometime get enough momentum off one hill as to get a long way up the next....
If your back is a bit fragile, you'd probably want one with at least rear suspension to isolate your back from road shocks - on mine I'll still occasionally get some buzz off the road but it has to be a fairly bad surface. The suspension on some bents is aimed more at taking out bigger hits, rather than the smaller stuff, tho' mine seems to make a decent job of both
Some trikes nowadays also have front suspension, that might give a little more isolation - bear in mind with a trike you've got 3 wheel lines which you need to steer around potholes, vs a single line on a two-wheeler.
Filtering through traffic is easier on higher 2-wheelers, whilst it's not impossible on a trike I'm not sure *I'd* want to - that was the reason for me getting a 2-wheeler rather than a trike.
Trikes don't fall over
- eg ice or slippy conditions - and are way easier wrt to hill starts, or even just spinning a ridiculously low gear up hills should you need to, without any stability issues. Oh, and like a go-kart on the way back down
Here in the SE there's:
Futurecycles in East Sussex handle ICE trikes (mebbe Optima too?), London Recumbents handle Challenge and Hase - and are very helpful and have Dulwich park to ride around in. Bikefix in central London handle Challenge and HPVelotechnik. There's a guy - Kevin at DTek in Ely (nr Cambridge) who's also very helpful and has a huge number of s/h 'bents to try/hire - he supplies ICE and Barchetta. He can also talk for England - tho' in an interesting way ! - so expect to be there a while
I'm one of the riders with a relatively minor condition - I can't ride a bike with bars lower than a typical mtb (and sometime not even then) without the neck muscles going into spasm. Mine (hpvelo. speedmachine) was a choice of not so low as to make filtering difficult, whilst low enough to avoid busting anything in a fall (you don't get much change to catch a slide), plus suspension front/back, and a rather adjustable seat. Oh, and underseat steering rather than above seat, since I've had some problems with ulnar nerve compression in the elbow in the past. But it's not light...